Controlling caller ID with Remote-Party-ID privacy setting

Discussion in '3CX Phone System - General' started by nwhitfield, May 21, 2010.

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  1. nwhitfield

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    I'm doing acceptance testing on a SIP trunk, and have run into an issue with calls from numbers that are supposed to be withheld.

    The telco is sending the caller's number in the SIP invite, and using the privacy option in the Remote-Party-ID header to indicate that the number has been withheld, ie with privacy=full

    Telco maintains this is the correct way to do it (rather than change the caller's number to 'anonymous' in the invite), but how do I then get 3CX to ensure that the number isn't presented to the extensions?
     
  2. SY

    SY Well-Known Member
    3CX Support

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    Re: privacy headers ignored?

    Please provide following information:
    1. the name of the telco
    2. Should PBX hide the number? Are you sure?
    3. What is exact business case where 3CX phone system should not show Caller ID when delivers call from external source to local user?

    Thanks
     
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  3. nwhitfield

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    Re: privacy headers ignored?

    The telco is Gamma (a UK operator)

    The calls are dialled by users on the PSTN, who have used the prefix (141) in the UK to indicate that their number should not be released to the person they are calling. Calling any other PSTN line, or a mobile, would show 'private number' or 'withheld' or some similar message.

    The PBX should act in the same manner; if a caller has chosen to withhold their number, then the only people who should be able to obtain it are the police or other appropriate authorities, surely.

    While other providers change the number in the SIP headers to 'anonymous', Gamma seem to be using the 'privacy' flag instead.

    The result is that anyone who choses to call me, when using 3CX with Gamma's SIP trunk, no longer has the option of withholding their number. If the privacy flag is set to 'full' on an incoming call it seems to me it would be logical (and in accordance with the wishes of the original caller) for 3CX to act on that, and discard the incoming number.

    Here's an incoming call, where the PSTN caller has withheld their number (last six digits of number replaced by x)

    INVITE sip:01962xxxxxx@94.30.55.100 SIP/2.0
    Via: SIP/2.0/UDP 83.245.6.81:5060;branch=z9hG4bKfb8a39a6567f3ffb0473dcf68bf8b521
    Max-Forwards: 69
    Contact: <sip:07973xxxxxx@83.245.6.81:5060>
    To: <sip:01962xxxxxx@83.245.6.81:5060>
    From: <sip:07973xxxxxx@83.245.6.81>;tag=3483458609-959590
    Call-ID: 3235168-3483458609-959584@MSX12.gammatelecom.com
    CSeq: 1 INVITE
    Expires: 180
    Session-Expires: 3600;refresher=uac
    Allow: INVITE, BYE, OPTIONS, CANCEL, ACK, REGISTER, NOTIFY, INFO, REFER, SUBSCRIBE, PRACK, UPDATE
    Call-Info: <sip:83.245.6.81>;method="NOTIFY;Event=telephone-event;Duration=1000"
    Supported: timer, 100rel
    Allow-Events: telephone-event
    Content-Length: 0
    Remote-Party-ID: <sip:7973xxxxxx@83.245.6.81>;party=calling;screen=yes;privacy=full

    Where a caller hasn't chosen to withhold their number, the incoming request is identical, save for the RPID, which looks like this:

    Remote-Party-ID: <sip:7973xxxxxx@83.245.6.81>;party=calling;screen=yes;privacy=off
     
  4. SY

    SY Well-Known Member
    3CX Support

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    Re: privacy headers ignored?

    1. PBX MUST show all Caller IDs delivered by the external systems to the local users.
    2. Gamma MUST NOT introduce this number if it is requested by the initiator of the call.
    3. "Remote-Party-ID" is NOT standard header (please correct me if I'm wrong) and MUST NOT influence the rule 1.

    The question:
    is still actual. Please don't ignore it.

    Thanks

    P.S. 07973xxxxxx and 7973xxxxxx are different numbers. What are you trying to debug?
     
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  5. leejor

    leejor Well-Known Member

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    Re: privacy headers ignored?

    It is up to the provider (phone company) to respect the requested call block and NOT pass the number, in any form, onto the called party. I would pursue this with Ofcom under privacy concerns and see if here is not some sort of law that should prevent them from doing this, or perhaps is it just an oversight on their part that needs correcting. http://www.ofcom.org.uk/complain/
     
  6. nwhitfield

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    Re: privacy headers ignored?

    07973xxxxxx and 7973xxxxxx are both (in full) the same number; in the second case, Gamma has stripped the inital 0 from it. Quite why they do that, I don't know.

    But what I'm trying to debug is whether or not 3CX can be told not to display the caller ID, based on the privacy setting in the headers supplied with the incoming call from Gamma Telecom

    Remote-Party-ID doesn't seem to be in any of the RFCs, but has been in various IETF drafts, which is probably why it gets used by people - for example, it's described in http://tools.ietf.org/html/draft-ietf-sip-privacy-04 and more briefly at http://www.z9hg4bk.org/sip/hf/remote-party-id.html and it was also use in at least some versions of Cisco software too.

    Gamma seem to be taking the view that they will deliver the number, but with the flag set to indicate that it should be hidden. Now, I'm sure there could be a long argument about the rights and wrongs of that, but that's the way they're doing it.

    As for your question about business case, I'm afraid I don't even know what it means, so I can't begin to answer it.

    All I can say is that, if there is a header, even if just a draft, that VoIP providers use to indicate the wishes of PSTN callers about privacy of their number, shouldn't it be respected somehow?
     
  7. nwhitfield

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    Re: privacy headers ignored?

    That would have been my initial thought too, frankly. I don't understand quite why they are simply setting the headers and hoping for the best, because it means anyone who wants to find out who's calling just needs a SIP trunk and they can read all the information. And, frankly, I'm glad that it seems I'm not missing something on that point; I'm relatively new to VoIP, though not to the concepts of data protection and privacy, and wondered if I'd missed some finer point of configuration.

    I will be getting back to them about this, not least because it would just be so much simpler if they did just pass the call down the trunk as anonymous. But even so, if there were a way to look at those headers in 3CX, that too would surely be an advantage, wouldn't it?
     
  8. leejor

    leejor Well-Known Member

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    I'm wondering if they could be held legality liable if they allowed a phone number to go through and the caller assumed (and rightly so) that it was blocked? Say, in the case of a battered wife. I would pursue this if I were you. Can you say, lawsuit?
     
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